This invention relates to fire retardant compositions. In one of its aspects, this invention relates to the production of fire-retardant compositions. In another of its aspects, this invention relates to the production of compositions that will impart fire retardance to cellulose-based insulation. In another of its aspects, this invention relates to methods for preparing monoammonium phosphate (MAP). In still another of its aspects this invention relates to a method for preparing MAP having a polyphosphate content in the range of up to about 10 weight percent.
During recent years, the need to conserve all forms of energy usage has greatly increased. To help meet this need the insulation industry has sought to provide insulation of improved quality. As a result, various types of insulation have been used such as glass fibers, foams, cellulose, etc. In addition to the insulating qualities of the various products, there should exist, either inherently or through additives, other important performance properties such as fire retardancy. Providing fire retardancy through use of additives is especially important for cellulose-based insulation products. Monoammonium phosphate is reported in such U.S. Pat. Nos. as 2,935,471 and 3,334,045 as an important ingredient in producing fire retardant insulation compositions based on cellulose.
The ammonium phosphates are prepared by the addition of ammonia to phosphoric acid, the latter of which is produced by either an electric furnace process or by a wet acid process. The electric furnace process is more expensive but products obtained are purer and, thus, more desirable for fire retardant compositions. The wet acid process is more economical but produces many impurities and, therefore, is largely restricted to use for the production of both liquid and solid fertilizers. It would be of great economic impact to use the fertilizer grade ammonium phosphate and the process equipment to produce fire retardant grade monoammonium phosphate. Unfortunately, fertilizer grade ammonium phosphate contains large amounts of diammonium phosphate which is undesirable as a fire retardant ingredient because of its low decomposition temperature. In addition, liquid fertilizer grade ammonium phosphate contains high levels (e.g., 65 weight percent) of polyphosphates that help to solubilize or stabilize the liquid fertilizer solution by sequestering metal impurities. Polyphosphates are undesirable from a fire retardant standpoint because they are hygroscopic and tend to impart high levels of moisture, and thereby cause tackiness on the surface of the cellulose insulation to which they have been applied. Higher forms of ammonium phosphate such as heptammonium phosphate, (NH.sub.4).sub.7 H.sub.2 (PO.sub.4).sub.3, can be separated from fertilizer ammonium phosphate solutions which can then be converted to monoammonium phosphate in reasonably pure form for possible use in fire retardant compositions. However, this process which is described in U.S. Pat. No. 3,420,623 is a multi-step process subject to many process controls which increase production costs and chances for error.
In view of the difficulties mentioned, there exists a need for making available lower cost monoammonium phosphate with a polyphosphate content sufficiently low that it can be used as an ingredient in fire retardant chemical compositions.
It is therefore an object of this invention to provide a method for imparting fire retardance to a cellulose-based insulating material. It is another object of this invention to provide methods for producing monoammonium phosphate (MAP), particularly MAP having a polyphosphate content in the range of up to about 10 weight percent. It is still another object of this invention to provide fire retardant, cellulose-based insulating materials.
Other aspects, objects, and the various advantages of this invention will become apparent upon studying this disclosure, the appended claims, and studying the drawings.